The present invention relates to apparatus for dispensing liquid, normally in discrete small quantities or charges. The invention has particular application to the dispensing of liquid from replaceable cartridges which may contain grit for scouring purposes.
One type of soap dispenser is disclosed in U.S. Pat. No. 4,108,363 and includes a flexible pump bowl which receives soap from a container through a diaphragm-type check valve. When the bowl is compressed it closes the check valve and forces the soap in the bowl out through a passageway to a discharge outlet. This structure is relatively complex and is not well suited to modern distribution networks which require field maintenance by unskilled laborers, nor is it suited to the dispensing of soap containing grit, since the grit tends to clog the passageways in the device thereby increasing maintenance problems.
A similar type of dispenser using a compressible pump bowl or nipple is disclosed in U.S. Pat. No. 1,326,880, the dispenser ejecting soap directly from a slit in the pump nipple. This dispenser utilizes a custom-made check valve stopper in the soap container outlet, and depends on distortion of the slit in the nipple for dispensing of soap therefrom. Thus, the nipple is compressed in the direction of the slit. This has the disadvantage that the slit can be opened permitting soap to drip therefrom before pressure in the nipple has been raised sufficiently to close the check valve.
Another type of soap dispenser is which includes mechanisms for dispensing discrete quantities of liquid soap. A problem which has been encountered in most of the prior art soap dispensing devices is that repeated discharges of the dispensing mechanism of the soap result in less than full quantities of soap being discharged after the initial operation. Basically this is because there is insufficient venting of the soap container or cartridge so that refill into the discharge nozzle or nipple is not sufficient for providing a full dosage when such soap dispensers are subjected to repeated rapid uses, as is common in public washrooms and the like.
Various soap dispensing systems have been proposed which solve the problem of providing full dosage for each dispensing operation by establishing an air passage between the inside of the soap container and the outside so as to continually provide full atmospheric pressure within the soap container irrespective of the number of discharge sequences.
For example, in U.S. Pat. No. 4,646,945, issued to Robert L. Steiner et al, there is disclosed a vented discharge assembly for a liquid soap dispenser including a valved vent opening separate from the outlet opening for the liquid soap for providing a vent path through the discharge assembly while effectively preventing discharge of liquid soap through the vent path. However, if the pump was depressed with excessive force, it was possible to pump the soap product past the valve and out the air intake opening, and the buildup of dried soap in the intake area could result in blockage of the air vent path.
Another vented discharge assembly for a liquid soap dispenser, disclosed in U.S. Pat. No. 4,930,667 (Ser. No. 299,934) issued to Charles R. Holzner, includes a semipermeable filter mounted between the discharge assembly and the soap container to introduce air into the soap container immediately upon withdrawal of soap from the container to permit rapid operation of the discharge assembly. The filter comprises a disc-shaped semi-permeable membrane installed in the air passageway which is offset radial-y from the liquid soap outlet opening. However, the air passageway has a relatively small cross section making it susceptible to becoming blocked as the result of soap drying on the filter membrane. Thus, it would be desirable to have a liquid dispensing system including a vented cartridge in which the air passageway is not susceptible to blockage.
Another problem that is inherent in this field is the use of unauthorized replacement cartridges in the dispensers. That is, although the dispenser is designed to accept a specific cartridge, third parties often attempt to enter the replaceable cartridge market and bootleg inferior soap products into the dispenser.
To avoid unauthorized cartridges being used in dispensers, anti-bootleg devices have been included in the dispenser mechanism to prevent the use of unauthorized cartridges therein. Examples of soap dispensers including anti-bootleg devices are disclosed, for instance, in Steiner et al U.S. Pat. Nos. 4,391,309 and 4,429,812. However, these prior art soap dispensers employ a dispensing pump mechanism which is integral with the housing which defines a reservoir from which soap is drawn in use. The cartridge is adapted for mounting on the housing and supplies soap to the reservoir by gravity. The anti-bootleg mechanism comprises a plurality of keys located in the inlet opening of the reservoir which prevent proper seating of unauthorized cartridges. In the event that a bootlegger attempts to use a standard cylindrical necked cartridge, the cartridge will not seat properly and soap will run out of the dispenser. However, such arrangement would not be usable in the liquid dispenser of the present invention wherein the pump mechanism is part of the container.